Internet Sharing (Bridging) Tiger to Leopard Doesn't Work

I can't believe I'm the only one with this problem, but no matter where I post, no one has anything to offer.

Can someone PLEASE tell me why I can share my ethernet connection from a Leopard to a Tiger box via Airport, but not vice versa (i.e. ethernet from Tiger to Leopard via Airport). There is no router involved. There is a modem and two computers. That's it, nothing else to fuss with. It used to work both ways, but now only works one way.

I guess, I wasn't quite clear in my post, but I tried to say, I'd tried it both ways and that it only worked if ethernet was plugged into a Leopard box being shared to the Tiger computer via Airport, but not with ethernet plugged into the Tiger one to be shared with the Leopard one via Airport.

Ethernet -> Leopard -> Airport -> Tiger = Good Connection!

Ethernet -> Tiger -> Airport -> Leopard = No connection!

The Airpot icon in menu bar in the wirelessly connected (sic) computer, however, shows good, strong connection either way!

If you will be patent I will try it here and get back to you. I have an issue here where I live that I have to take care of but later I promise I will try it both ways and report back. It really should work either way.

Is there a reason you need it the way it does not work like the system with Leopard is where the Modem is?

Also what Machines are you running Leopard and Tiger on? That might help just in case.

You guessed it! The Tiger box is an iMac and thus less portable than the MacBook running Leopard. It used to work. I'm sure I could buy a wireless router to obviate the problem, but, again, it used to work.

The fact that I can't find anyone with this exact problem would have me tending to think it's something on my end, but I think, I've tried every possible permutation available to me. Anyway, I'm curious what you might be able to suss out. I appreciate the consideration. Thanks!

I did my testing but just realized after reading your message I did not do it the way you are. I was using my WiFi Access Point in between for the WiFi part. It worked both from Leopard to Tiger and Tiger to Leopard though. I will try it the way I know you are doing and get back to you.

You are using the iMac with tiger itself to transmit the Wifi to the Laptop.

Only thing here it will be a PowerMac G4 1.8Giz with built in Airport doing Tiger and an iBook G4 running leopard to pick up the WiFi from the Power Mac.